Whooping cough bacterium (Bordetella pertussis), illustration. These rod-shaped Gram-negative bacilli cause whooping cough, known as pertussis, mainly in infants. This infectious disease of the respiratory tract produces fits of coughing that end in loud inspiratory whoops. Potentially fatal in newborn and premature babies, these bacteria are spread in coughed droplets. Antibiotic drugs have a limited effect and the disease must run its course; a pertussis vaccination is effective.